Shielding of electronic articles is becoming increasingly important with the continued expansion and use of proximally located electronic equipment. All electronic equipment emits electromagnetic radiative or conductive energy which may produce electromagnetic interference (EMI). The presence of EMI from proximal electronic sources is particularly problematic for highly sensitive electronic equipment such as that found in targeting systems and electronic systems used for space flight.
Generally two methods are used for protecting electronic equipment from EMI. The simple process of identifying non-compatible proximal or distant radiative sources and removing them or increasing their distance was a typical method of protection. The method of avoiding or removing EMI sources is not available when a sensitive electronic device is mobile and it is not possible to predict the environment in which the device will be used.
The second method is to provide a conductive shielding that is electrically grounded to direct electronic energy away from the article to be protected. Many methods of shielding against EMI have been introduced including a conductive mesh or grid that is layered on a structural substrate. These methods are illustratively found in U.S. Patent Application Publication 2007/0084631, the contents of which are incorporated herein by reference. Metalized fabrics where one or more metal coatings are layered on a woven, nonwoven, or open mesh carrier backing or substrate has also been proposed as described in U.S. Pat. Nos. 4,900,618; 4,910,072; 5,075,037; 5,393,928; and 6,652,777, the contents of each of which are incorporated herein by reference. Finally, coatings such as conductive inks can be applied to a film or flexible or solid substrate. Water-based conductive inks for these purposes are illustratively found in U.S. Pat. Nos. 5,286,415 and 5,389,403 the contents of each of which are incorporated herein by reference.
Each of the prior materials and processes are inadequate for use in transportable shielding articles where ruggedness, low weight, and adequate shielding are desirable. The coatings are susceptible to scratching, denting, or other deformation altering their conductive abilities and creating gaps in any shielding that may allow both ingress and egress of electromagnetic energy. These gaps, dents, or damaged sections may also compromise the efficiency of the connection to ground.
Thus, there exists a need for materials and articles that are structurally operable, transportable, and have reduced susceptibility to damage.